Not all upgrades happen without problems
Some people may be having problems with accessing email on independent email servers over the Telstra mobile service. The number of faults has been significant and it seems that this will continue through the weekend until Monday. This upgrade is to expand the mobile network capacity to handle extra subscribers but of course this means that some services will be interrupted.
In the meantime, customers are encouraged to use webmail services to check email or access email over other services than Telstra mobile.